The technical field of this disclosure relates to automatic shut-off valves, and their methods of operation; and more particularly to a fire hydrant safety shut-off valve. Above ground, street mounted fire hydrants have been known to be broken away from their underground water supply systems when struck by a vehicle. In such cases, a large flow of water may be released from the water system into the street before system water can be shut off. A wet barrel hydrant is normally held at water system pressure all the time. Such hydrants are known to provide a breakaway interconnection with a water system riser, allowing the hydrant to break off from the water system riser upon collision, and thus minimizing damage to the water system's pipes and flanges and minimizing loss of water. It is known to provide a valve between a breakaway flange or breakaway riser and a water system riser which is able to stop the flow of water from the system upon a breakaway event, in some cases, backflow from the street takes place, so that contaminated water enters the water supply system. The prior art teaches both linear axial shutoff valves and flapper valves including dashpot dampened valves to lessen water hammer. What is not found in prior art hydrant automatic shutoff apparatus is a valve that is simple in design, mountable between a water system riser and a hydrant having a breakaway flange ring or riser, and which is able to act to prevent uncontrolled flow of system water from the broken hydrant system while acting also as a check valve to prevent backflow of contaminated water from running into the water system riser. Additionally the prior art does not teach valve closure rate control to avoid water hammer. The presently described valve and valve disclosure teaches a novel automatic shutoff valve with these features and which has other structural distinctions and benefits therefrom as will be explained.
Like reference symbols in the drawing figures indicate like elements.